Deferred grazing back in play

That’s the view of AgResearch scientist Dr Katherine Tozer who was at Fieldays this month talking to farmers about this option. The concept is not new and some of the early research dates to the 1950s and 1960s by one of the early ag scientists, Eddie Suckling. In 1951 he presented a paper at the Grasslands conference showing the success of over-sowing pastures in autumn as opposed to spring.

In recent years there has been a revival of this concept, coming with the support from the likes of DairyNZ and Beef+Lamb NZ. To that end, Tozer and others have done further research to fill in gaps from early investigations into this pasture management tool.

Put simply, deferred grazing is about resting or locking up a limited amount of the grazing platform for a period between mid to late spring and late summer. Tozer says in the case of dairy, this could be up to10% of the pasture and maybe slightly longer for sheep and beef farmers, depending on their individual feed and water availability. The overall aim of the system is to improve pasture quality and at Fieldays there was significant interest in this option.

She says this involves the farmer assessing what grass species – such as plantain or other mixtures – will be best, and then over-sowing these on the ‘deferred paddocks’.

“When the stock are brought in to eat the deferred pasture, they will trample in the seed and ensure that it has good soil contact and will establish easily. It also means that as the grass is eaten down, the seeds will have light – necessary for growth, but also some protection from the remaining grass,” she says.

The advantage of this, says Tozer, is that the longer grass in the paddock will retain soil moisture which is good for germinating the seed. She says the longer grass will also prevent the paddock from drying out too quickly.

About The Research

The aim of the research by Katherine Tozer and others is to get some hard data on the benefits of deferred grazing. She says for example they are interested in seeing how the system improves root depth, pasture resilience and if it has any impact on carbon sequestration.

“So, we have got two sites [with] rhizotrons installed. These are clear plastic tubes inserted at an angle into the ground, and with the aid of a camera we can measure of root growth over time to see how it’s changing, in terms of seasonal growth, and how deferred grazing is having an impact as opposed to not using deferred grazing,” she says.

Tozer says one issue of concern raised about deferred grazing is the risk of facial eczema due to dead grass in paddocks where spores are commonly found. She says their research shows that when spore counts occurred in deferred grazing pasture, these were much lower than in conventional pasture.

For Tozer and advocates of deferred grazing, the message at Fieldays to farmers was ‘give it a go’. Start small and trial the idea to see how it works. She says it may not be for everyone, but is a good option – with one proviso. Tozer says deferred grazing will likely not work in a paddock where browntop or weeds are very dominant. She says browntop is very difficult to work with and paddocks that are already good will benefit most from deferred grazing and will likely improve profitability.